Sealed rolling bearing

ABSTRACT

A sealed rolling bearing has sealing devices with both the functions of high sealing ability and small sliding resistance, which are antipodal to each other. The sealed rolling bearing has an outer member ( 1, 30 ) formed with an outer raceway surface ( 8, 29 ) on its inner circumferential surface. An inner member ( 4, 5, 32 ) is formed with an inner raceway surface ( 9   a   , 9   b   , 31 ) on its outer circumferential surface. The inner raceway surface ( 9   a   , 9   b   , 31 ) is arranged opposite to the outer raceway surface ( 8, 29 ). Rolling elements ( 10, 34 ) are freely rollably contained between the outer and inner raceway surfaces. Sealing devices ( 12, 13, 35 ) are arranged in an annular space formed between the outer and inner members ( 1, 30  and  4, 5, 32 ). Each of the sealing devices ( 12, 13; 35 ) has elastic sealing lips ( 27   a   ˜27   c   , 23˜25, 37   a   , 37   b ). The maximum height Ry or Rmax of the surface roughness of a sliding surface of a member of the rotational side ( 18, 4, 32 ), which the sealing lips ( 27   a   ˜27   c   , 23˜25, 37   a   , 37   b ) slidingly contact, is limited to a value of 2.0 μm or less. The run-out of the sliding surface, normal thereto, is limited to a value of 30 μm or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2004/015711, filed Oct. 22, 2004, which claims priority toJapanese Patent Application No. 2003-367307, filed Oct. 28, 2003 andJapanese Patent Application No. 2004-004245, filed Jan. 9, 2004. Thedisclosures of the above applications are incorporated herein byreference.

FIELD

The present invention relates to a sealed rolling bearing used inautomobiles, motors in general use etc., and, more particularly, to asealed roller bearing used under circumstances where a great deal ofwater, muddy water and many other foreign matter exist.

BACKGROUND

In general, sealed roller bearings, with high sealability, preventingress of rain water or dusts into the inside of the bearing. Thebearings are used, for example, as bearings for the suspension ofautomobiles. This is due to the fact that these bearings are usuallyexposed to severe conditions which contain muddy water, dusts etc. Onthe other hand, such a rolling bearing is required to have a smallrotational torque since a large rotational torque on the bearing causesadverse influence to bearing temperature rise and fuel consumption.Since the sliding resistance of the seals is a major factor thatinfluences an increase in the rotational torque of the bearing, it isdesirous to provide a sealed rolling bearing that has not only a highsealability but a small sliding resistance.

One representative example of such a bearing for an automobile isdescribed with reference to FIG. 1. FIG. 1 shows a first embodiment ofthe present disclosure. This bearing is used for a driving wheel of anautomobile. The bearing includes an outer member integrally formed witha body mounting flange on its outer circumference. The flange is adaptedto be mounted on a body (not shown) of the automobile. The outer memberis also formed with double row outer raceway surfaces on its innercircumferential surface. A wheel hub has an integrally formed wheelmounting flange on one of its end to mount a wheel (not shown). Oneinner raceway surface is formed on the outer circumferential surface ofthe wheel hub. The inner raceway surface is arranged opposite to one ofthe double row outer raceway surfaces. A cylindrical portion, of asmaller diameter, axially extends from the inner raceway surface. Thecylinder portion includes serrations formed on its inner circumferentialsurface to transmit torque. An inner ring is adapted to be fitted on thecylindrical portion and the inner ring includes the other inner racewaysurfaces formed on its outer circumferential surface.

Double row rolling elements (balls) are arranged between the double rowouter and inner raceway surfaces. The balls are freely rollably held bycages. Sealing devices are arranged at both ends of the outer memberwithin an annular space formed by an inner member (including the wheelhub and the inner ring) and the outer member. The sealing devicesprevent leakage of grease contained within the bearing as well asingress of rain water or dusts into the inside of the bearing.

The sealing device of the inboard side, arranged between the outermember and the inner ring, includes a sealing ring with a metal core.The metal core has a substantially L-shaped cross-section and is fitinto the outer member. A sealing member is integrally adhered, viavulcanized adhesion, onto the metal core. A slinger, having a similarL-shaped cross-section, is fit onto the inner ring. The sealing memberis made of an elastic material, such as rubber, and has three sealinglips, an outer sealing lip, a middle sealing lip and an inner sealinglip. The tip edge of the outer sealing lip is in sliding contact with aninner side of an upstanding portion of the slinger. The tip edges of themiddle sealing lip and the inner sealing lip are in sliding contact witha cylindrical portion of the slinger.

The sealing device, on the outboard side, has an annular metal core anda sealing member integrally adhered, via vulcanized adhesion, on themetal core 26. The sealing member is made of elastic material, such asrubber, and has three sealing lips. The tip edges of the three sealinglips are in direct sealing contact with the surface of the wheel hub.

In the sealing devices of the bearing for a wheel of a vehicle of theprior art, the slinger of the sealing device on the inboard side has asurface roughness of a sliding surface on which the sealing lips slidingcontact which is limited to a value at the center line average height(Ra) at 0.3 μm or less and to a value at the maximum height (Ry) at 1.2μm or less. Thus, foreign materials cannot easily enter into the insideof the bearing. This is due to the difficulty to generate a small gap atthe maximum height portions and damages which would be otherwise causedat rolling contact portions by change in the properties of the grease(see Japanese Laid-open Patent Publication No. 184897/2003).

However, in order to limit the surface roughness of a sliding surface towhich the sealing lips sliding contact to the value at the center lineaverage height (Ra) at 0.3 μm or less and to the value at the maximumheight (Ry) at 1.2 μm or less, it is necessary, previously, to presssheet members having the target surface roughness or to carry outlapping of the surfaces of sheet members after the pressing process. Infact, since availability of the plate member with such a target surfaceroughness is difficult, it is state of art, in view of its manufacturingcost, to carry out lapping of the surfaces of the sheet members afterthe pressing process.

Such a lapping of the surface of the slinger makes its handling verydifficult, increases the number of processing steps, and further causesdeformation of the surface of the slinger. Such a deformation of thesliding surface of the slinger causes variation of the interference ofthe sealing member. This reduces the following ability of the sealinglips and accordingly reduces the sealing of the bearing.

SUMMARY

It is, therefore, an object of the present disclosure to provide asealed rolling bearing with sealing devices which provide both functionsof high sealability and small sliding resistance, which are antipodal toeach other.

To achieve the object mentioned above, a sealed rolling bearingcomprises an outer member with outer raceway surfaces formed on itsinner circumferential surface. An inner member is formed with innerraceway surfaces on its outer circumferential surface. The inner racewaysurface is arranged opposite to the outer raceway surface. Rollingelements are freely rollably contained between the outer and innerraceway surfaces. Sealing devices are arranged in an annular spaceformed between the outer and inner members. Each of the sealing deviceshas sealing lips formed from an elastic member. The maximum height Ry orRmax of the surface roughness of a sliding surface of a member of therotational side which the sealing lips sliding contact is limited to avalue of 2.0 μm or less. The run-out of the sliding surface, normalthereto, is limited to a value of 30 μm or less.

Since each of the sealing devices has sealing lips formed from anelastic member and the maximum height Ry or Rmax of the surfaceroughness of the sliding surface of a member of the rotational sidewhich the sealing lips sliding contact is limited to a value of 2.0 μmor less, and the run-out of the sliding surface normal thereto islimited to a value of 30 μm or less, it is possible to suppress theabsolute irregularities of the sliding surface to a small variation.Also, it is possible to suppress variation of the interference withoutincreasing the interference of the sealing member. This avoids theproblem of deformation of the sliding surface which is caused by thelapping of the slinger. Accordingly, it is possible to stabilize thefollowing ability of the sealing lips relative to the sliding surfaceand thus further improve the sealability.

It is preferable that the sealing device includes a sealing ring mountedon a member of the stationary side and a slinger mounted on a member ofthe rotational side. The sealing lips, forming the sealing ring, are insliding contact with the slinger. This structure makes it unnecessary tostrictly restrict the target surface roughness by applying a lappingprocess to the sliding surface after the pressing process. Thus, it ispossible to improve the sealability by only setting the run-out of thesliding surface at a predetermined value.

Also, the sealing device includes a sealing ring mounted on a member ofthe stationary side, side lips and a radial lip. The sealing lips are indirect sliding contact with the member of the rotational side. Thisstructure makes it possible to easily carry out surface machining, suchas grinding or lapping, of the sliding surface after heat treatment evenif the target surface roughness and the run-out are not obtained.

Further, the sealing device includes a sealing ring mounted on a memberof the stationary side, a main lip and a sub lip. The main lip is indirect sliding contact with a sealing groove formed on a member of therotational side. The sealing groove has a substantially U-shapedcross-section. The sub lip is in sliding contact with a ridge of thesealing groove, via a small interference. This structure makes itpossible to increase the interference, while keeping the sealingability, due to the following ability of the sub lip when the main lipwears. Accordingly, it is possible to suppress the rotational torque ofthe bearing during a small amount of wear of the main lip as well as toobtain the sealing ability due to an increase of interference inaccordance with the wear of the main lip.

Also, preferably the maximum height Ry or Rmax of the surface roughnessof the sliding surface is limited to a value of 1.2 μm or less. Therun-out of the sliding surface, normal thereto, is limited to a value of10 μm or less. This provides a sealed rolling bearing with sealingdevices which has both functions of high sealing ability and smallsliding resistance, which are opposite to each other.

The sealed rolling bearing includes an outer member formed with outerraceway surface on its inner circumferential surface with outer racewaysurface. An inner member is formed with an inner raceway surface on itsouter circumferential surface. The inner raceway surface is arrangedopposite to the outer raceway surface. Rolling elements are freelyrollably contained between the outer and inner raceway surfaces. Sealingdevices are arranged in an annular space formed between the outer andinner members. Each of the sealing devices has elastic member sealinglips. The maximum height Ry or Rmax of the surface roughness of asliding surface of a member on the rotational side, which the sealinglips sliding contact, is limited to a value of 2.0 μm or less. Therun-out of the sliding surface, normal thereto, is limited to a value of30 μm or less. This makes it possible to suppress the absoluteirregularities of the sliding surface to a small variation as well as tosuppress variation of the interference without increasing theinterference of the sealing member. Thus, this avoids the problem ofdeformation of the sliding surface which is caused by lapping of theslinger. Accordingly, it is possible to stabilize the following abilityof the sealing lips relative to the sliding surface and to furtherimprove its sealing ability.

A sealed rolling bearing includes an outer member with outer racewaysurface formed on its inner circumferential surface; an inner memberformed with inner raceway surface on its outer circumferential surfacearranged opposite to the outer raceway surface; rolling elements freelyrollably contained between the outer and inner raceway surfaces; andsealing devices arranged in an annular space formed between the outerand inner members. Each of the sealing devices has elastic membersealing lips. The maximum height Ry or Rmax of the surface roughness ofa sliding surface of a member of the rotational side, which the sealinglips sliding contact, is limited to a value of 2.0 μm or less. Therun-out of the sliding surface, normal thereto is limited to a value of30 μm or less.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

Additional advantages and features of the present disclosure will becomeapparent from the subsequent description and the appended claims, takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is a longitudinal-section view of a first embodiment of a sealedrolling bearing according to a first embodiment.

FIG. 2 is a partially enlarged sectional view of the sealing device ofthe inboard side of the sealed rolling bearing according to the firstembodiment.

FIG. 3 is a partially enlarged sectional view of the sealing device ofthe outboard side of the sealed rolling bearing according to the firstembodiment.

FIG. 4 is a longitudinal-section view of a sealed rolling bearingaccording to a second embodiment.

FIG. 5 is a partially enlarged sectional view of a sealing device of asecond embodiment.

FIG. 6 is a graph showing results of mass variation in a muddy waterproof test carried out by exposing a naked bearing, itself, to the muddywater.

DETAILED DESCRIPTION

Preferred embodiments of the present invention will be described withreference to accompanied drawings.

FIG. 1 is a longitudinal-section view of a first embodiment of a sealedroller bearing. The sealed rolling bearing shown in FIG. 1 is an exampleapplied to a driving wheel of a vehicle for rotatably supporting thewheel in a suspension of the vehicle. Since the fundamental structure ofthe bearing provided with the sealing devices previously mentioned hasbeen described at the beginning of this specification using FIG. 1,characteristic portions of the bearing will be mainly describedhereinafter.

Sealing devices 12 and 13 are arranged at either ends of an annularspace formed between the outer member 1 and inner member 3, comprised ofthe wheel hub 4 and the inner ring 5 which form a member of therotational side. The outer member 1 forms a member of the stationaryside. The sealing devices 12 and 13 prevent leakage of grease containedwithin the bearing as well as ingress of rain water or dusts into theinside of the bearing.

The sealing device 12 mounts between the outer member 1 and the innerwheel 5 on the inboard side (the right hand side in FIG. 1). The sealingdevice 12, as shown in FIG. 2, includes a sealing ring 17 with a metalcore 15. The metal core 15 has a substantially L-shaped cross-section.The sealing device 12 is fit into the outer member 1. A sealing member16 is integrally adhered, via vulcanized adhesion, onto the metal core15. A slinger 18, with a similar L-shaped cross-section, is fit onto theinner ring 5. The slinger 18 and the metal core 15 are made by pressforming of austenitic stainless steel sheet (JIS SUS 304 etc.) orpreserved cold rolled sheet (JIS SPCC etc.).

The sealing member 16 is made of an elastic material such as rubber andincludes three sealing lips, an outer sealing lip 23, a middle sealinglip 24 and an inner sealing lip 25. The tip edge of the outer sealinglip 23 sliding contacts an inner side of an upstanding portion 22 of theslinger 18. The tip edges of the middle sealing lip 24 and the innersealing lip 25 are in sliding contact with cylindrical portion 21 of theslinger 18. The surface roughness of a sliding surface of the slinger18, which the sealing lips 23, 24 and 25 are in sliding contact with, islimited to a value of 2.0 μm or less, and preferably at 1.2 μm or lessat the maximum height Ry or Rmax. The run-out of the sliding surface,normal thereto, is limited to a value of 30 μm or less, and preferablyat 10 μm or less. Accordingly, it is unnecessary to strictly restrictthe target surface roughness by applying a lapping process to thesliding surface after the pressing process as in the prior art. This isachieved only by setting the run-out of the sliding surface at apredetermined value.

Thus, it is possible to suppress the absolute irregularities of thesliding surface to a small variation as well as to suppress variation ofthe interference without increasing the interference of the sealingmember. Thus, this avoids the problem of deformation of the slidingsurface of the slinger 18 which is caused by lapping the slinger as inthe prior art. Accordingly, it is possible to stabilize the followingability of the sealing lips 23, 24 and 25 relative to the slidingsurface and to further improve the sealability.

The sealing device 13 on the outboard side, as shown in FIG. 3, includesan annular metal core 26 and a sealing member 27 integrally adhered, viavulcanized adhesion, on the metal core 26. The metal core 26 is formedby press forming of austenitic stainless steel sheet (JIS SUS 303 etc.)or preserved cold rolled sheet (JIS SPCC etc.). The sealing member 27 ismade of an elastic material, such as rubber, and includes two side lips(dust seal) 27 a, 27 b and one radial lip (grease seal) 27 c. The tipedges of the sealing lips 27 a˜27 c are in direct sliding contact withthe surface of the wheel hub 4. The tip edges contact a sliding surface19 on the base of the wheel mounting flange 7 on the inboard side.

The maximum height Ry or Rmax of the surface roughness of the slidingsurface 19, which slidingly contacts the sealing lips 27 a, 27 b and 27c, is limited to a value of 2.0 μm or less, and preferably at 1.2 μm orless. The run-out of the sliding surface 19, normal thereto, is limitedto a value of 30 μm or less, and preferably at 10 μm or less. If thesetarget surface roughness or run-out cannot be obtained, a grinding orlapping process may be conducted on the sliding surface after it is heattreated.

Thus, similar to the sealing device 12, it is possible to suppress theabsolute irregularities of the sliding surface 19 to a small variationas well as to suppress variation of the interference without increasingthe interference of the sealing member. This avoids the problem ofdeformation of the sliding surface. Accordingly, it is possible tostabilize the following ability of the sealing lips 27 a, 27 b and 27 crelative to the sliding surface 19 and to further improve its sealingability.

FIG. 4 is a longitudinal-section view of a sealed rolling bearingaccording to a second embodiment of the present disclosure. FIG. 5 is apartially enlarged sectional view of FIG. 4. The sealed rolling bearing20, exemplary shown in FIG. 4, is a deep groove ball bearing. An outerring 30 is formed with an outer raceway surface 29 on its innercircumferential surface. An inner ring 32 is formed with an innerraceway surface 31 on its outer circumferential surface. Balls 34 arecontained and freely rollably held by a cage 33 between the outer andinner raceway surfaces 29 and 31. A pair of sealing rings 35 arearranged in an annular space formed between the outer and inner rings 30and 32.

Each of the sealing rings 35 has a metal core 36 with flat annularconfiguration formed from cold rolled steel sheet (JIS SPCC etc.) bypress forming. A sealing member 37 is integrally adhered, via vulcanizedadhesion, onto the metal core 36. The sealing rings 35 are fit into theinner circumferential surface at both ends of the outer ring 30, via thesealing members 37. Each of the sealing members 37 is in direct slidingcontact with a sealing groove 38. The sealing groove 38 has asubstantially U-shaped cross-section formed at each end on the outercircumferential surface of the inner ring. A main lip 37 a of thesealing member 37 contacts an inclined sliding surface 39 of the sealinggroove 38. A sub lip 37 b of the sealing member 37 contacts a ridge 40of the sealing groove 38, via a small interface. The base of the sub lip37 b has a constricted cross-section. Thus, the sub lip 37 b has a smallflexural rigidity. Accordingly, the sub lip 37 b can follow the motionof the main lip 37 a and move toward the left hand direction (FIG. 5) inaccordance with the wear of the main lip 37 a. Thus, this increases theinterference relative to the ridge 40. The sub lip 37 b can suppress therotational torque of the bearing during a small wearing amount of themain lip 37 a and can ensure its sealing ability while increasing theinterference relative to the ridge 40 in accordance with wear of themain lip 37 a.

The maximum height Ry or Rmax of the surface roughness of at least thesliding surface 39 of the sealing groove 38, which the main sealing lip37 a slidingly contacts, is limited to a value of 2.0 μm or less, andpreferably at 1.2 μm or less. The run-out of the sliding surface 39,normal thereto, is limited to a value of 30 μm or less, and preferablyat 10 μm or less. If these target surface roughness or run-out cannot beobtained, a grinding or lapping process may be conducted on the slidingsurface after it is heat treated.

Thus, it is possible to suppress the absolute irregularities of thesliding surface 39 to a small variation as well as to suppress variationof the interference without increasing the interference of the sealingmember. Thus, this stabilizes the following ability of the sealing lip37 a relative to the sliding surface 39 and further improves its sealingability.

FIG. 6 is a graph showing results of mass variation in a muddy waterproof test carried out by exposing a naked bearing, itself, to the muddywater. This test was carried out by spraying Kanto foam JIS 8 mixedliquor onto samples of sealed rolling bearings of the present disclosureand the prior art during driving, and then measuring the mass variationbefore and after the test. As can be seen from FIG. 6, there areremarkable differences between sample 1 (Comparative example) having themaximum height Ry or Rmax of 2.02˜3.7 μm and the run-out of 30 μm normalto the sliding surface 39, sample 2 (Embodiment A) having the maximumheight Ry or Rmax of 1.3˜1.86 μm and the run-out of 10˜30 μm normal tothe sliding surface 39, and sample 3 (Embodiment B) having the maximumheight Ry or Rmax of 0.7˜1.2 μm and the run-out of 10 μm or less normalto the sliding surface 39.

The sealed rolling bearing of the present disclosure can be applied toany type of sealed rolling bearings, irrespective of its bearing orsealing type, used under circumstances where a large amount of foreignmatter, such as water or muddy water, exists.

The present disclosure has been described with reference to thepreferred embodiment. Obviously, modifications and alternations willoccur to those of ordinary skill in the art upon reading andunderstanding the preceding detailed description. It is intended thatthe present invention be construed to include all such alternations andmodifications insofar as they come within the scope of the appendedclaims or their equivalents.

1. A sealed rolling bearing comprising: an outer member formed with atleast one outer raceway surface on its inner circumferential surface; aninner member formed with at least one inner raceway surface on its outercircumferential surface, said inner raceway surface with inner racewaysurface arranged opposite to the outer raceway surface; rolling elementsfreely rollably contained between the outer and inner raceway surfaces;and sealing devices arranged in an annular space formed between theouter and inner members, each of the sealing devices has sealing lips ofan elastic member, said sealing lips being in sliding contact with asliding surface of a member of a rotational side, the maximum height Ryor Rmax of the surface roughness of said sliding surface of the memberof the rotational side is limited to a value of 2.0 μm or less, and therun-out of the sliding surface, is limited to a value of 30 μm or less.2. The sealed rolling bearing of claim 1 wherein one of said sealingdevice mounted on a member of a stationary side and a slinger mounted ona member of the rotational side, and the sealing lips forming a sealingring in sliding contact with the slinger.
 3. The sealed rolling bearingof claim 1 wherein said sealing device mounted on a member of astationary side, including sealing side lips and a radial lip, thesealing side and radial lips directly slidingly contact the member ofthe rotational side.
 4. The sealed rolling bearing of claim 1 whereinsaid sealing device mounted on a member of a stationary side, includes amain lip and a sub lip, the main lip directly sliding contacts a sealinggroove formed on a member of the rotational side, said sealing groovehaving a substantially U-shaped cross-section, and the sub lip slidinglycontacts a ridge of the sealing groove via a small interference.
 5. Thesealed rolling bearing of claim 1 wherein the maximum height Ry or Rmaxof the surface roughness of the sliding surface is limited to a value of1.2 μm or less, and the run-out of the sliding surface, normal thereto,is limited to a value of 10 μm or less.